Monday: Weather forecast for Key West Race Week

Quantum Key West 2014 has attracted 129 entrants for a full week of racing (Jan. 20-24) in Key West, FL. Located at the southernmost tip of the continental United States, and just 90 miles from Cuba, having a handle on the weather is a challenge and a key to success at this elite event. Here is the weather forecast prepared by Sailing Weather Service issued 0700 LT 20 January 2014

WARNINGS AND ADVISORIES: There are no active warnings or advisories posted for the sailing area today. Conditions can change quickly. Please monitor NOAA All Hazards Radio on your VHF for the latest official warnings and advisories from The National Weather Service.

SYNOPSIS: The regatta will start with a very light breeze today before improving moderately tomorrow before becoming fresh on Wednesday. The rest of the week should see mainly moderate breezes.

This morning’s weather map shows a very minor cold front extending across southern FL and into the southeastern Gulf of Mexico just to the north of Key West. At the same time, weak high pressure is holding west of Key West with a ridge extending eastward across the lower keys and into the northern Bahamas this morning. This ridge means that gradient are nearly nonexistent this morning, so that forcing for the breeze is weak.

The ridge axis is expected to remain south of Key West today. The minor cold front will likely weaken and dissipate before reaching the Keys and therefore is expected to that limited or no real impact. Later this afternoon, a broader Westerly gradient may start to infiltrate across the course area. This will be the first indication that a pre-frontal gradient is developing ahead of a cold front moving out of the central US and toward the Gulf. This front is not expected to reach Key West until Tuesday night.

CURRENT CONDITIONS: Winds are very light across the lower keys this morning (mainly less than 5 knots), but the direction is consistent from the SSW/SW. The breeze has been light all night, trending slightly right from S to SSW most recently.

Satellite show scattered to broken cloud cover over the area. Radar has a few hits of very weak/light showers north of Key West. There could be a few drop of rain out of any clouds over the islands, but nothing of significance.

FORECAST DISCUSSION: Light and variable winds are forecast this morning, mainly from the S/SW less than 5 knots. There will be a trend for winds veering more SW/W this morning, but speeds are likely to hold light 3-7 knots. Very patchy conditions. A period of calm or variable wind is possible mid-day through early afternoon, with some courses having a light, but inconsistent breeze and other glassing off. During the afternoon, watch for a possible W/NW trend of very light 4-8 knot winds developing, especially after about 1400.

WEATHER: Partly to mostly cloudy this morning. There is a very small chance (< 10%) of a few very light showers or even just sprinkles of rain this morning. Then becoming mainly sunny with just a few minor cumulus clouds around from later this morning through the afternoon.

TEMPERATURE: Low-60sF this morning, warming to low-/mid-70sF this afternoon.

SEAS: Generally 1 ft or less, mostly as a minor swell over open waters and little wind chop.

Detailed Wind Forecast:
Time Wind Speed Wind Direction (MAG)
(LT) Mean Range Mean Range
0800 04 01-07 220 200-240
0900 05 02-07 230 210-250
1000 06 03-08 245 220-260
1100 05 03-07 250 225-270 …quite variable and patchy
1200 04 02-07 Variable
1300 04 02-07 Variable …patchy and unstable/variable
1400 06 04-08 270 245-290 …¦chance of winds holding more left
1500 07 04-09 275 250-295
1600 08 05-10 285 260-305 …chance lighter and more left
1700 08 05-10 280 260-300
1800 08 05-09 280 260-300

HEDGE: FORECAST CONFIDENCE: BELOW AVERAGE

1) While there is high confidence that today will be very light, the details of the forecast table become less reliable since the very light airs can make the wind meander in direction. As a result, I have put a low confidence in for today, since wind direction could easily fall out of range at times.
2) The various forecast models are in agreement on the light winds, however some are slightly more optimistic in getting a light (but sailable) breeze while others suggest insufficient wind for sailing all day. I favored the lighter models, but gave a nod to the possibility of sailable breeze by pushing up the high end of the wind speed range.
3) Regardless, you should expect a very patchy and unstable wind out there today. I do not expected sailing in any wind much over 9 knots. Most likely sailing wind range 4-8 knots for the day.
4) Again, the least reliable part of the forecast is wind direction. I have given my best guess on the trend (right), but random oscillations and shifts out of range are likely. These have low predictability, so keeping eyes on the weak wind pattern around the course will be very important.
5) There is an outside chance that winds will hold SW all day, without the predicted right trend. If wind speeds hold more left and doesn’t die off in the mid-day transition shown in the forecast table, then it will very likely remain more SW all day, but still very light.
6) Any clouds over the course area today are likely to kill the breeze. There may be localized puffs at the edges of cumulus clouds, but these will be short-lived.

***************************************************************
OUTLOOK FOR TUESDAY (21 January 2014)
Still forecasting a developing breeze through the day. A strong cold front is expected to be working its way southeast across the eastern Gulf of Mexico through the day. The front will not cross Key West until later Tuesday night, however winds will be increasing in the pre-frontal gradient which will be veering from SW to NW through the day.

Increasing moisture ahead of the front is expected to lead to more cloud and an increased risk of rain showers through the day. The chance of rain showers occurring in the sailing area at some point during the racing day is about 50%.

Detailed Wind Forecast:
Time Wind Speed Wind Direction (MAG)
(LT) Mean Range Mean Range
0800 10 08-12 250 230-270
1000 09 07-12 260 245-275 …perhaps becoming veery patchy
1200 12 09-14 275 255-290 …right shifting breeze with a build possible
1400 14 11-16 290 275-305
1600 15 12-17 300 280-315
1800 15 13-17 310 290-325

SEAS: Slight becoming moderate chop 1-3 ft in the afternoon.

TEMPERATURE RANGE: Near 60F / Mid 70sF

WEATHER: Increasing clouds with a chance of showers developing especially late morning onward. The risk of showers will increase with time through the afternoon.

***************************************************************
OUTLOOK FOR WEDNESDAY (22 January 2014)
The strong cold front will move across Key West overnight , bringing an abrupt right shift NNW/N and increasing winds with some very gusty conditions. Winds will be strongest in the morning, then a slow veering and easing trend in the post-frontal gradient is forecast to moderate winds and seas in the afternoon.

WIND: NNW/N in the morning, building 20-25 kts for a time mid-morning. A gradual veer to the N is expected from later morning through the afternoon. Chance of winds easing 15-20 kts during the afternoon.

SEAS: Very rough 3-6 ft. Roughest further offshore near the bottom of the courses. Seas subsiding slowly through the afternoon.

TEMPERATURE RANGE: Much cooler. Near 60F / Mid-60sF

WEATHER: Some broken cloud cover and a slight chance of showers in the early morning. Then clearing to partly cloudy conditions in the morning.

***************************************************************
OUTLOOK FOR THURSDAY (23 January 2014)
Weakening high pressure moves across FL, with moderating winds and seas veering NE/E with time. A late backing to NE or NNE is possible.

WIND: NE/ENE 8-13 in the morning, possible 11-15 for a time. Winds may veer further to ENE/E in the afternoon, however also watching for a possible left shift late in the afternoon. Timing is uncertain.

SEAS: 2-3 ft.

TEMPERATURE RANGE: Near 60F / Low-70sF

WEATHER: Mainly sunny. Some cumulus cloud offshore over the Gulf Stream in the AM. Cumulus develop on the upper keys in the afternoon and may drift offshore toward the course areas PM.

***************************************************************
OUTLOOK FOR FRIDAY (24 January 2014).
No change from yesterday’s outlook. Another Arctic High pressure plunging into the deep south will reinforce the N/NE gradient, with stronger winds likely at least in the morning. The gradient will veer in the afternoon and an easing trend is forecast.

WIND: N/NE building 15-20 knots through late morning, then tending NNE/NE and easing 12-17 kts in the afternoon. Possibly lighter by later afternoon.

SEAS: Very rough 3-5 ft in the morning, moderating 2-4 ft in the afternoon.

TEMPERATURE RANGE: Near 60F / Low-/Mid-70SF

WEATHER: Some scattered to broken cloud in the morning with a slight chance of showers. Then becoming mostly sunny.